This invention relates generally to control area networks (CANs) for managing the operation of internal combustion engines, and more specifically to systems for synchronously controlling a plurality of such engines. The invention is disclosed in the context of a multiple trailer road train vehicle, but is believed to be useful in other applications as well.
In some internal combustion engine applications, the required power output to drive a load exceeds the capability of a single engine and drive train combination. Some examples of such applications are generator sets, boats having twin propulsion screws, multi-engine aircraft, and multiple trailer road train vehicles. For these and other applications, engine synchronization systems are known in the art. For example, a mechanical device for synchronizing marine engines is described in the Herbert U.S. Pat. No. 3,258,927 granted Jul. 5, 1966, herein incorporated by reference. In the Sturdy U.S. Pat. No. 4,964,276 granted Oct. 23, 1990, herein incorporated by reference, an electronic synchronizer is described for controlling the speed of a second engine to maintain it in synchronism with a master speed signal from a first engine. In the Bernardi U.S. Pat. No. 5,771,860 granted Jun. 30,1998, herein incorporated by reference, another electronic synchronizer is described for controlling the power output from a second engine as a function of three variables. The three variables are the inlet manifold pressure of a first engine, the inlet manifold pressure of the second engine, and a signal produced by an offset potentiometer that compensates for minor differences between the manifold-pressure-to-power-output ratios of the two engines.
Most prior art systems designed to synchronize a plurality of engines involve monitoring the speed of a master engine and adjusting the speed of one or more slave engines to match the speed of the master engine. For engines driving a common load, control based on engine speed only functions properly if the engines and drive trains are identical. That is, at any engine speed, the torque output by each engine to the driven member (wheels, drive shaft, screw, etc.) must be the same. While these engine speed-based control methods are adequate for controlling identical engines, they do not provide a user with the ability to control engines having differing power and torque characteristics and drive-train configurations.
One method of synchronizing engines which does not use engine speed as the controlling parameter is shown in Bernardi. In the Bernardi patent, a system is disclosed for synchronizing the power output of two mechanically-linked engines, where the first engine transmits mechanical power through a shaft to the second engine, and the second engine transmits mechanical power to a load, such as an electrical generator. However, as summarized above, the disclosed method adjusts the throttle of a second engine as a function of the inlet manifold pressures of the two engines; the controller attempts to maintain equal manifold pressures in the two engines. This system assumes manifold pressure is a proxy for power output and engine speed. This assumption is only valid if the engines are identical, or near enough to identical that the disclosed offset potentiometer may compensate for the difference.
While these and other prior art systems generally perform adequately for the applications for which they are designed, they do not provide a means for controlling engines having differing power output and torque output characteristics, so that the engines may be adapted to drive a common load.
According to one aspect of the invention, a control system is provided for use with at least a first engine producing a first torque and second engine producing a second torque. The control system comprises an interface between a first control computer associated with the first engine and a second control computer associated with the second engine. The first control computer is configured to control the second control computer through the interface such that the second torque is a function of the first torque.
Illustratively according to this aspect of the invention, the first engine has a first maximum torque output associated therewith. The interface receives a first percent torque message indicating a first percentage that equals the first torque divided by the first maximum torque. The interface generates a torque request message indicating a requested torque value indicating a requested torque to be produced by the second engine that is a function of the first percentage, and transmits the torque request message to the second control computer.
Further illustratively according to this aspect of the invention, the second engine has a second maximum torque output associated therewith. The interface receives a second percent torque message indicating a second percentage that equals the second torque divided by the second maximum torque output. The requested torque value is further a function of the second percentage.
Alternatively illustratively according to this aspect of the invention, the interface receives a first message indicating a first value from the first control computer and a second message indicating a second value from the second control computer. The interface calculates an error value indicating the difference between the first and second values. The interface utilizes this error value to calculate a requested torque value indicating a requested torque to be produced by the second engine to cause the error value to approach zero.
Further illustratively according to this aspect of the invention, the interface transmits a torque request message indicating the requested torque value to the second control computer.
Additionally illustratively according to this aspect of the invention, the interface provides a torque request signal indicating the requested torque value to the second control computer.
Additionally illustratively according to this aspect of the invention, the first value indicates a percentage that equals the first torque divided by the first maximum torque output.
Additionally illustratively according to this aspect of the invention, the first value indicates a brake mean effective pressure produced by the first engine.
Alternatively illustratively according to this aspect of the invention, the first control computer is coupled to a first network. The second control computer is coupled to a second network. The interface is coupled between the first and second networks.
According to another aspect of the invention a control system is provided for synchronizing the operation of a plurality of internal combustion engines. The system comprises, a first control computer associated with a first internal combustion engine, the control computer producing a first datum. The system further comprises a second control computer associated with a second internal combustion engine. The system further comprises an interface operatively coupled between the first and second control computers. The interface is responsive to the first datum to provide an operational command to the second control computer. The second control computer is responsive to the operational command to control the second engine, so that a first relationship exists between a second torque produced by the second engine and a first torque produced by the first engine.
Additionally illustratively according to this aspect of the invention, the first internal combustion engine has a first maximum torque output associated therewith. The first datum indicates a first percentage that equals the first torque divided by the first maximum torque output.
Further illustratively according to this aspect of the invention, the second internal combustion engine has a second maximum torque output associated therewith. The second control computer produces a second datum indicating a second percentage that equals the second torque divided by the second maximum torque output. The interface is further responsive to the second datum to provide the operational command to the second control computer so that the first relationship is further a function of the second percentage.
Alternatively illustratively according to this aspect of the invention, the first datum indicates a first value. The second control computer produces a second datum indicating a second value. The interface is responsive to the first and second data to produce an error value indicating the difference between the first and second values. The interface calculates a requested torque value indicating a requested torque to be produced by the second internal combustion engine to cause the error value to approach zero.
Further illustratively according to this aspect of the invention, the operational command comprises a torque request message indicating the requested torque value.
Further illustratively according to this aspect of the invention, the operational command comprises a torque request signal indicating the requested torque value.
Further illustratively according to this aspect of the invention, the first engine has a maximum torque output associated therewith, and the first value indicates a percentage that equals the first torque divided by the maximum torque output.
Further illustratively according to this aspect of the invention, the first value indicates a brake mean effective pressure produced by the first engine.
Alternatively illustratively according to this aspect of the invention, the first control computer is coupled to a first network. The second control computer is coupled to a second network. The interface is coupled between the first and second networks.
Alternatively illustratively according to this aspect of the invention, the interface is operatively coupled to a selector having at least a first and a second state. The first relationship exists between the first torque and the second torque when the selector is in the first state. A second relationship exists between the first torque and the second torque when the selector is in the second state.
According to another aspect of the invention a slave control computer is provided for controlling a slave engine. The slave control computer comprises a first interface adapted to receive a datum from a master engine control computer associated with a master engine, and a second interface adapted to provide a fueling signal to a fueling system associated with the slave engine. The fueling system is responsive to the fueling signal to provide a quantity of fuel to the slave engine so that a second torque produced by the slave engine is related to a first torque produced by the master engine.
According to another aspect of the invention a master control computer for controlling a master engine. The master control computer comprises a first interface adapted to provide a fueling signal to a fueling system associated with the master engine. The fueling system is responsive to the fueling signal to provide a quantity of fuel to the master engine. The master control computer comprises second interface adapted to provide a datum to a slave control computer associated with a slave engine. The slave control computer is responsive to the datum to control the slave engine so that an output torque produced by the slave engine is related to an output torque produced by the master engine.
According to another aspect of the invention a control system is provided for use with at least a first engine producing a first torque and a second engine producing a second torque. The control system comprises a first control computer configured to compute a first fueling signal, a first fueling system responsive to the first fueling signal to supply a corresponding quantity of fuel to the first engine, a second control computer configured to compute a second fueling signal, a second fueling system responsive to the second fueling signal to supply a corresponding quantity of fuel to the second engine, and an interface operatively coupled between the first and second control computers. The interface is responsive to a first datum from the first control computer to provide an operational command to the second control computer. The second control computer is responsive to the operational command to compute the second fueling signal so that the second torque is a function of the first torque.
Illustratively according to this aspect of the invention, the first engine has a first maximum torque output associated therewith. The first datum indicates a first percentage that equals the first torque divided by the first maximum torque output.
Further illustratively according to this aspect of the invention, the second engine has a second maximum torque output associated therewith, the second control computer produces a second datum indicating a second percentage that equals the second torque divided by the second maximum torque output, and the interface is further responsive to the second datum to provide the operational command to the second control computer so that the second torque is further a function of the second percentage.
Alternatively illustratively according to this aspect of the invention, the first datum indicates a first value. The second control computer produces a second datum indicating a second value. The interface is responsive to the first and second data to produce an error value indicating the difference between the first and second values and to provide the operational command such that the error value approaches zero.
Further illustratively according to this aspect of the invention, the operational command is a torque request message.
Alternatively illustratively according to this aspect of the invention, the operational command is a torque request signal.
Alternatively illustratively according to this aspect of the invention the second engine has a second maximum torque output associated therewith, and the first value indicates a percentage that equals the first torque divided by the maximum torque output.
Alternatively illustratively according to this aspect of the invention, the first value indicates a brake mean effective pressure produced by the first engine.
Alternatively illustratively according to this aspect of the invention, wherein the first control computer is coupled to a first network, the second control computer is coupled to a second network, and the interface is coupled between the first and second networks.
According to another aspect of the invention, an apparatus is provided for controlling a first torque output of a first engine having a first electronic control module that produces a first control signal to control a first fueling system associated with the first engine, and a second torque output of a second engine having a second electronic control module that produces a second control signal to control a second fueling system associated with the second engine. The apparatus comprises an input port coupled to the first electronic control module to receive a reference datum from the first electronic control module, the reference datum correlating to the first torque output, a feedback port coupled to the second electronic control module to receive a feedback datum from the second control module, the feedback datum correlating to the second torque output, an output port coupled to the second electronic control module, and a controller coupled to the input, feedback, and output ports. The controller is responsive to the reference datum and the feedback datum to generate an output signal that is indicative of changes to be made to the at least one second control signal in order for the second torque output to match the first torque output. The controller transmits the output signal to the second electronic control module via the output port.
Illustratively according to this aspect of the invention, the controller is configured to subtract the feedback datum from the reference datum to produce a difference signal, and to process the difference signal to generate the output signal.
According to another aspect of the invention, a motor vehicle system is provided. The motor vehicle system comprises a tractor including a main engine, a first plurality of wheels, and a torque-request device coupled to the main engine. The torque-request device sends a torque-request signal to the main engine. The main engine operates to supply a first torque to at least one of the plurality of wheels to propel the vehicle in response to the torque-request signal. The motor vehicle system further comprises a trailer coupled to the tractor. The trailer includes an auxiliary engine and a second plurality of wheels. The auxiliary engine is operable to supply a second torque to at least one of the second plurality of wheels. The motor vehicle system further comprises a controller coupled to the main engine and coupled to the auxiliary engine. The controller receives from the main engine a first signal indicative of the first torque and from the auxiliary engine a second signal indicative of the second torque. The controller is configured to process the first and second signals and to produce a third signal indicative of changes to be made to the second torque so that the second torque is a function of the first torque. The controller provides the third signal to the auxiliary engine. The auxiliary engine is responsive to the third signal to modify the second torque.
According to another aspect of the invention, a method is provided for synchronizing a plurality of torque producing engines. The method includes receiving a first signal from a first control computer associated with a first engine, receiving a second signal from a second control computer associated with a second engine, processing the first and second signals to produce a third signal indicative of changes to be made to a second torque produced by the second engine so that the second torque is a function of a first torque produced by the first engine. The method further includes providing the third signal to the second control computer. The second control computer is responsive to the third signal to control the second engine such that a brake mean effective pressure of the second engine is a function of a brake-mean effective pressure of the first engine.